Here's how to override the shift lock on a 2006 Monte Carlo. First, remove the top of the shift console by pulling up on the plastic piece directly in front of the hinged cover. This is the piece that has the cup holders molded into it and it is held in place by 4 clips (i.e. it will pop back into place with no tools).

Next, shine a flashlight down into the console to the right of where the shift lever passes through (passenger's side). You'll see a wiring clip with 4 or 5 wires going into it. Directly behind this clip you can see a metal shaft with a flared top that looks like a button. This is the shift lock override button. Reach in behind the wiring clip with your right hand and press this button in. With the engine running, hold the button in with your right hand, press on the brake, and shift out of park with your left hand.

Now you can drive the car to your mechanic (or to your own garage) to find out why the shift lock solenoid is not working. On mine it was obvious. A wire going into that clip near the override button came loose and there was no power to the shift lock solenoid. I removed the clip, reattached the wire, and replaced the clip. Problem solved, fixed for free!